On sudden unexpected immersion in cold water 15 degrees celsius or lower, there is an uncontrollable gasping for breath followed by severe hyperventilation (rapid breathing).  This on its own can cause small muscle spasms and drowning.

Upon entering dangerously cold water, blood is pulled away from the skin and shunted it to the centre of the body in an effort to maintain core temperature.  This rush of cold blood to the heart may cause cardiac arrest.  Along with this, there is a massive increase in heart rate and blood pressure which can cause death, particularly in older, less healthy people. These effects last for two to three minutes.

Wearing a lifejacket during the unexpected immersion is critically important to keeping you afloat and breathing.   Death from cold-water shock is not uncommon.

Recovery of the victim from the water should be attempted as quickly as possible. Handle the victim gently to avoid cardiac arrest.

The victim should minimize movement while in the water and adopt a fetal position with legs together and knees raised, with arms to the side, or folded across the chest to prolong survival time.

Once out of the water, the victim should be treated the same as a hypothermia victim. See the next topic, Hypothermia.